Xiao-jian Tian

Pseudo-random sequence generator based on the generalized Henon map

By analysis and comparison of several chaotic systems that are applied to generate pseudo-random sequence, the generalized Henon map is proposed as a pseudo-random sequence generator. A new algorithm is created to solve the problem of non-uniform distribution of the sequence generated by the generalized Henon map. First, move the decimal point of elements in the sequence to the right; then, cut off the integer; and finally, quantify it into a binary sequence. Statistical test, security analysis, and the application of image encryption have strongly supported the good random statistical characteristics, high linear complexity, large key space, and great sensitivity of the binary sequence.

Design of a rectangular patch antenna with a photonic crystal substrate

Abstract Patch antennas have many advantages such as low profile, conformity to planar, etc. However, as they couple power into surface-wave modes, patch antennas have low gain and low radiation efficiency. The photonic crystal (PC), due to its frequency bandgap, can diminish the surface-wave modes significantly and thus improves the gain, radiation efficiency and directivity. In this paper, a patch antenna with a PC substrate is designed and analyzed using the software package high frequency structure simulator (HFSS). The results show that the antenna with a PC substrate has a lower return loss, a higher gain and a lower side lobe level, compared with the conventional antenna.

Soliton molecules in a fiber laser mode-locked by a graphene-based saturable absorber

We have experimentally investigated a novel kind of soliton molecule in a graphene-based mode-locking fiber laser with anomalous dispersion. The soliton molecule exhibits a stable rectangular profile on the oscilloscope, whereas it shows randomly distributed peaks in the autocorrelation trace, which indicates that the temporal separation of pulses in the molecule is varying all the time. The optical spectrum is modulated with a depth of about 7 dB over the whole profile, induced by the interaction of the intra-molecule solitons. The experimental results demonstrate that solitons in the pulse molecule oscillate randomly in temporal domain and the neighboring molecules are temporally separated by a fundamental cavity repetition rate, which is very different from that of the multi-solitons or bound-state solitons.

Observation of Dissipative Bright Soliton and Dark Soliton in an All-Normal Dispersion Fiber Laser

This paper proposes a novel way for controlling the generation of the dissipative bright soliton and dark soliton operation of lasers. We observe the generation of dissipative bright and dark soliton in an all-normal dispersion fiber laser by employing the nonlinear polarization rotation (NPR) technique. Through adjusting the angle of the polarizer and analyzer, the mode-locked and non-mode-locked regions can be obtained in different polarization directions. Numerical simulation shows that, in an appropriate pump power range, the dissipative bright soliton and dark soliton can be generated simultaneously in the mode-locked and non-mode-locked regions, respectively. If the pump power exceeds the top limit of this range, only dissipative soliton will exist, whereas if it is below the lower bound of this range, only dark soliton will exist.

Simulation study on hyperchaos analysis of reforming system based on single-ring erbium-doped fiber laser

Abstract A reforming dynamic system based on the single-ring erbium-doped fiber laser is proposed in this paper. The reforming system has larger Lyapunov exponent and better pseudorandom characteristics according to the simulation results. It is promising in the application of the image encryption and secret communication.

Study on large time-delay constant temperature control system based on TEC

Abstract This paper designes a diminutive constant temperature control system based on thermoelectric cooler (TEC). Considering that the system is a large time-delay control system, the paper proposes a new method to determine the transfer function of the controlled system which gets the transfer function by doing nonlinear fitting of the step response of the controlled system. The characteristics of system model which is established by the method are basically same as the actual constant temperature control system. This method provides a new way of thinking to the design of large time-delay control system.

On the temperature characteristics of phase measurement in homodyne fiber interferometer

Abstract Different from the traditional way of using piezoelectric (PZT) phase shifter to measure phase difference, a new method is designed to calculate it between signals in the two arms of a homodyne fiber interferometer. A simple homodyne fiber interferometer system is then established to measure the interference photocurrent and the photocurrents from the two fiber arms generated by the signal power on a temperature control plat. The homodyne fiber interferometer system is composed of fiber and sensitive to the variation of temperature. Thus, is necessary to study the temperature characteristics in the phase measurement of homodyne fiber interferometer. The experimental results show that the variation of the phase difference of signals in the two fiber arms is proportional to the variation of temperature.

Research and design of the protection circuits in LD controller

According to the parameters and applications of laser diode (LD), three protection circuits were designed: the time-delay soft-start protection circuit, the power-on impulse protection circuit and the limit-current protection circuit. In this article, the structure and the principle of every protection circuit have been detailed. From several tests and feedbacks from customers, the expected goals have been completed.

Study on design and electro magnetic compatibility of high-power pulse driver

Abstract A kind of high-power pulse driver is designed to drive semiconductor laser. The circuit consists of three parts: generator of pulse signal, power amplifier of pulse signal and storage circuit controlled by metal-Oxide-semiconductor field-effect transistor (MOSFET). According to the experimental results, this kind of high-power pulse driver well restrained the pulse spike and overshoot by proper design, better choice of components and improvement of electro magnetic compatibility (EMC). The circuit can output pulse signal with better quality, which provides qualified driving signal to laser diode. The pulse width is under 50 ns and the output ranges from 10 A to 50 A.

Study on the influences of system parameters on bound self-similar pulse pairs in a passively mode-locked fiber laser

Abstract This paper is devoted to research the characteristics of the bound self-similar pulses formed in a passively mode-locked Yb-doped fiber laser. The parabolic shape bound self-similar pulses with linear chirps are observed in the fiber laser. The influences of the small signal gain and the inter-cavity average group velocity dispersion (GVD) on pulse separation, pulse duration, peak power and single pulse energy of the bound self-similar pulse pairs are investigated in-depth. The simulation results contribute to the study of the stable transmission of bound state pulses.